I. Field of the Invention
The present invention relates generally to potentiometers.
II. Description of the Related Art
Potentiometers are resistors in which the resistance is variable by adjusting a control device. For example, one type of potentiometer has a knob that is turned in one direction (e.g., clockwise) to increase the resistance and in the opposite direction to decrease the resistance. The resistance is typically measured between the wiper of the potentiometer and one of the end terminals.
One problem with potentiometers is that the resistance selected by adjusting the control is not readily apparent. A multi-meter is typically connected across the wiper connection and one end of the potentiometer in order to measure the change in resistance. If a voltage is coupled across the potentiometer, the multi-meter can be used to measure the change in voltage. In either case, a separate, bulky, measuring device is required in order to adjust the potentiometer accurately for a particular application. There is a need in the art for a potentiometer that can be accurately adjusted without a need for additional measuring equipment.
The present invention encompasses a digital potentiometer device. The device has a potentiometer, coupled to a reference voltage, that generates a voltage that is variable by adjusting a potentiometer control input.
A programmable, voltage-scaling function generates a scaled variable voltage and a scaled reference voltage from the potentiometer""s voltage and the reference voltage, respectively. An analog-to-digital converter generates a digital signal from the analog scaled variable voltage. In one embodiment, the analog-to-digital converter uses the scaled reference voltage as a voltage reference.
Two input switches are used to enter user variables. The user variables set the units to be used by the device controller circuit when displaying the analog-to-digital converter data that indicates the potentiometer position. The user variables also determine the amount of scaling performed on the variable and reference voltages by the scaling function.